Almost always Tasty updates will handle source code changes correctly (that is, after compiling), except when the viewport displays object that aren't there anymore. For example, when the child object has been renamed or when an aggregate holds less member than before. I understand where the error comes from (out of experience), however a starting user would not understand the root cause of this error.

!! This section threw error: Neither XXX nor any of its ancestor instances could handle the XXX message The path to the containing object is: (the :root :root-object-object) !!

Why isn't the update functionality set-up in a more robust way, by for example throwing away "old-timers" from the display-list?